52 TEST ACE A ATLANTICA. 



Lowe, from Madeira. Indeed he himself mentions that he 

 possesses Madeiran examples of the vespertina, differing in no 

 respect from the Azorean ones except that they are a little more 

 purpurascent, which is one of the most conspicuous features 

 which distinguishes the A. gracilis. However, the point, of all 

 others, by which the shell may be recognised consists in the 

 number and relative proportions of the denticles and plaits with 

 which its aperture is furnished, two (the lower one of which is 

 large and prominent), often increased to three, being on the 

 ventral paries, one on the columella, and from about one to four 

 within the outer lip. Apart however from these primary cha- 

 racters, the A. gracilis may be further known by being very 

 much smaller than the cequalis, as well as less ovate (or more 

 strictly fusiform) in outline, and not quite so solid in substance. 



Auricula bicolor. 



Auricula bicolor, Morel., Hist. Nat. des Acor. 209, t. 5. f. 7 



(1860) 



Drouet., Faun. Acor. 168 (1861) 



Alexia bicolor, Mouss., Faun. Mai. des Can. 136 (1872) 



Habitat Pico ; in salinis subsalinisque ad oras rivulorum, 

 rupibus saxisque adhserens. 



A species which has been found in saline and subsaline 

 places in the island of Pico, at those parts of the coast where 

 the rivulets empty themselves into the sea, so that, like the 

 cognate forms, it appears to live sometimes in salt water and 

 sometimes in fresh. It is identical with an Auricula which was 

 met with abundantly by Mr. Lowe and myself in the north of 

 Lauzarote, in the Canarian archipelago, and which agrees 

 almost precisely with some examples which I have received from 

 Marseilles as the ' A. myosotis, Drap.' ; but since it is possible 

 that the Marseilles shell may have been wrongly identified, I 

 prefer citing the present species under the name which was pro- 

 posed for it by Morelet. 



The A. bicolor is decidedly peculiar in tint, the pale horn- 

 coloured surface being more or less conspicuously darkened by 

 a rich purplish bloom, which sometimes quite covers the spire ; 

 and its aperture has usually but a single plait (which is large 

 and prominent) on the ventral wall, though there are occasionally 

 indications of a minute tubercle-like second one midway between 

 the former and the insertion of the peristome. Its whorls are 

 a little convex ; its extreme nucleus is generally pale, transpa- 

 rent, and tilted ; and the entire shell is rather thin and pellucid 

 (for an Auricula), having at first sight somewhat the appear- 

 ance of a Limncea. 



